Pyrite FeS2-C composite as a high capacity cathode material of rechargeable lithium batteries

摘要

Pyrite FeS2 is a promising cathode material for rechargeable lithium batteries because of its high theoretical capacity (894 mA h g(-1)), low cost and near-infinite earth abundance. However, the progress in developing viable Li/FeS2 batteries has been hampered by the poor cyclability of the FeS2 cathode. Aiming to improve the cyclability of the FeS2 cathode, we here report a facile method for the synthesis of FeS2-C composites by a one-pot hydrothermal reaction of FeSO4 and Na2S2 in the presence of carbon black, and examine the effect of composition on the structure of FeS2-C composites and the cycling performance of Li/FeS2 cells. It is shown that the added carbon not only surrounds the FeS2 surface but also penetrates into the entire FeS2 particle, forming continuously conductive networks throughout the FeS2 particle. However, introduction of carbon meanwhile increases the particle size of the FeS2 active material. These two factors lead to an improvement in the rate capability of Li/FeS2 cells while having little effect on the specific capacity and capacity retention of the FeS2 cathode. On the other hand, we show that the electrolyte plays an important role in affecting the cyclability of Li/FeS2 cells, and that the ether- and carbonate-based electrolytes affect the cycling performance of Li/FeS2 cells in their unique manners.